Polydimethylsiloxanes, polyalkylmethylsiloxanes and fluorinated alkylmethylsiloxanes are well known for their hydrophobicity. In a variety of applications it is desirable to incorporate dimethylsiloxane units into other macromolecular structures in order to increase oxygen permeability, release, emollient, or low temperature properties, but a greater degree of hydrophilicity is required in the final polymer compositions. For EXAMPLE, methacrylate functional polysiloxane-based structures can be utilized in pigment dispersion, lithographic, release coating and contact lens applications.
Often, functional low molecular weight polysiloxanes, such as a methacryloxypropyl functional polydimethylsiloxane or 3-methacryloxy-2-hydroxypropyl functional polydimethylsiloxane, are copolymerized with monomers such as methyl methacrylate (MMA) or more polar monomers, such as hydroxyethylmethacrylate (HEMA), glycerylmethacrylate acrylonitrile, dimethylacrylamide, or vinylpyrrolidone. If the polysiloxane domain is too large, particularly with polar monomers, molecular phase separation can occur, reducing mechanical properties or, in cases such as hydrated copolymers, yielding compositions that are cloudy and are not suitable for optical applications. On the other hand, reducing the number of siloxane units to prevent phase separation can make desirable properties, such as those associated with oxygen permeability or surface energy, unachievable.
However, tightly controlled structures with distinct molecular weights can be utilized to achieve these properties by providing the maximum number of siloxane units which do not cause phase or domain separation in the final polymer. More specifically, macromonomers (alternately denoted macromers), polymers having molecular weights of less than 5000, that contain one polymerizeable group, such as methacrylate, acrylate, 3-methacryloxy-2-hydroxypropyl, or vinyl on the alpha and/or omega position of a polydimethylsiloxane have been the preferred starting materials for many pigment dispersion, lithographic and contact lens applications. These macromonomers are formed either directly by terminating an anionic non-equilibrium ring opening polymerization of cyclosiloxanes with a functional chlorosilane, such as methacryloxypropyldimethylchlorosilane, or through intermediates formed by termination with dimethylchlorosilane and then functionalizing by hydrosilylation or additional synthetic steps. This type of polymerization is sometimes referred to as living anionic ring-opening polymerization or “living AROP.”
For example, monomethacryloxy-terminated polydimethylsiloxane can be formed by initiating the “living” polymerization of hexamethylcyclotrisiloxane with n-butyl lithium and quenching the reaction with methacryloxypropyldimethylchlorosilane. 3-Acryloxy-2-hydroxypropyl terminated polydimethylsiloxane can be formed by initiating the “living” polymerization of hexamethylcyclotrisiloxane with n-butyl lithium, quenching the reaction with dimethylchlorosilane followed by hydrosilylation with allylglycidyl ether, and finally adding acrylic acid catalyzed by a metal salt such as chromium acetate. Thus, the products of current art are low molecular weight polysiloxanes with a functional group at one terminus and a hydrophobic group derived from the anionic initiator, typically a butyl or methyl group. Patents describing methods which use these macromers as comonomers include U.S. Pat. Nos. 5,166,276; 5,480,634; 5,016,148; 5,179,187; 5,719,204; and 7,052,131.
Most efforts on “living” AROP have been dedicated to forming block co-polymers, as reviewed by I. Yilgor in Advances in Polymer Science, 86, 28-30 (1988). C. Frye and others at Dow Corning made the earliest reports on living AROP (see J. Org. Chem., 35, 1308 (1970)). Monomethacryloxypropyl terminated polydimethylsiloxanes produced by “living” AROP, such as the compound shown in structure (I), were first introduced to the US market in Silicon Compounds Register & Review, 4th edition, R. Anderson, B. Arkles, G. Larson Eds. Petrarch Systems, p. 271 (1987).

These materials are offered for sale under the trademarks MCR-M11 and MCR-M17 by Gelest Inc. (Morrisville, Pa.). Recent reviews by J. Chojnowski, in “Silicon Compounds: Silanes and Silicones” (B. Arkles, J. Larson, Eds, Gelest, p. 389-405 (2004) and G. Belorgney and G. and Silicones” (B. Arkles, J. Larson, Eds, Gelest, p. 389-405 (2004) and G. Belorgney and G. Sauvet in “Silicon Containing Polymers” (R. G. Jones, Ed; Kluwer, p. 43-78 (2000)) generally refer to this class of materials as ω-monofunctional polysiloxanes.
The general synthetic technique utilized in the prior art is to initiate a living polymerization of a ring-strained cyclotrisiloxane with an alkyllithium or lithium alkyldimethylsilanolate initiator and, after cyclic siloxane monomer is consumed, terminate the reaction via a capping reaction. In other variations, different monomers are fed to the living polymer before termination, or the living polymer may be doubled in molecular weight by coupling with a non-functional material, such as dimethyldichlorosilane.
Monofunctional materials are usually formed directly or indirectly by a capping reaction, i.e., in the case of methacrylate terminated materials, either capping with methacryloxypropyldimethylchlorosilane, as described in U.S. Pat. No. 5,672,671, assigned to Chisso, or by first forming a monohydride-terminated material by capping with dimethylchlorosilane and then performing hydrosilylation with allylmethacrylate. Additionally, monoepoxy terminated compounds, such as those reported in U.S. Pat. No. 4,987,203, assigned to Chisso, have been reacted with methacrylic acid to form 3-methacryloxy-2-hydroxypropyl terminated polydimethylsiloxanes. The expected alternate route achieved by hydrosilylating a hydride terminated polydimethylsiloxane with allyloxyhydroxypropylmethacrylate has also been demonstrated by Parakka et al (see WO 2006/102050). EXAMPLEs of amino-termination and functionalization are provided by Leir et al in U.S. Pat. No. 5,237,082 and Letchford in U.S. Pat. No. 6,031,060. While other monofunctional materials have been reported, such as J. Pickering, et al (U.S. Pat. No. 7,074,488), this technology does not yield linear materials that are monodisperse, but are analogous to what are generally referred to as monofunctional T-resins in silicone technology.